Wall-mounted filter arrangement for blocking high-frequency electromagnetic radiation

ABSTRACT

The invention relates to a filtering device with a filter housing which can accept a filter mat, is covered with a lamella grid on the outlet side and is fitted in an aperture in a mounting wall. RF screening is attained without altering the structure of the filtering device in that the surface of the filter housing is electrically conductive and inserted in the aperture in the mounting plate via an electrically conductive contact frame. The contact frame is electrically connected to the filter housing and the aperture in the mounting plate and there is an electrically conductive screening grid inserted or mounted in the filter housing or between the latter and a fan which can be linked thereto.

FIELD OF THE INVENTION

This invention is related generally to electromagnetic radiation and,more particularly, to filter arrangements that block such radiation.

BACKGROUND OF THE INVENTION

Filter arrangements that are inserted into a mounting wall are known inthe art. Many such filters are substantially structurally similar to oneanother, irrespective of whether they are constructed with or without afan. Insofar as is known, there are no such filters that have thecapability to exclude or block high-frequency (HF) electromagneticradiation. Given the requirements to use filters in sensitive andinterference prone electronic devices, a filter arrangement that wouldafford protection from HF radiation would be an important improvement inthe art.

OBJECTS OF THE INVENTION

It is an object of this invention to provide a filter arrangementovercoming some of the problems and shortcomings of devices of the priorart.

Another object of this invention is to provide a filter arrangement thatis HF-impervious. How these and other important objects are accomplishedwill be apparent from the following descriptions and from the drawings.

SUMMARY OF THE INVENTION

The invention involves a filter arrangement comprised of: (1) anassembly plate having an aperture in its center; (2) an electricallyconductive contact frame inserted into the aperture of the assemblyplate; (3) a filter housing having an outlet side, an inlet side and acenter opening, connected to the contact frame; (4) a filter mat placedin the opening in the filter housing; (5) an electrically conductivegrid located between the filter housing and the filter mat; and (6) alamellar screen covering the filter mat.

In a preferred embodiment of the invention, a fan is attached to theinlet side of the filter housing and the electrically conductive grid ispositioned between the filter housing and the fan. In a more specificversion of this embodiment, the fan has an outlet and inlet side and theinlet side of the fan is covered by a protective screen. In stillanother version, the fan projects through both the contact frame and theaperture of the mounting plate.

In another aspect of the invention, the filter housing is constructed ofplastic in which electrically-conductive material is mixed or which hasbeen "metallized" or vapor-coated with a conductive substance so as tobe electrically conductive. In another embodiment of the invention, thefilter housing has a receptacle formed into its outlet side and thefilter mat and grid are inserted into the receptacle.

In yet another aspect of the invention, the filter housing has acircumscribing fastening flange with fastening bore holes and screwspassing through the fastening bore holes to secure the filter housing tothe mounting plate. In a specific version of such preferred embodiment,the mounting plate has a contact surface surrounding the aperture andthe contact surface contains a plurality of screw receptacles arrangedaround the aperture.

In still another aspect of the invention, the inlet side of the filterhousing is covered by a mesh holding screen and such holding screensupports the grid and filter mat. The holding screen may be constructedin one piece together with the filter housing.

In yet another aspect of the invention, the contact frame projects intothe aperture of the assembly plate. The first and second edges of eachof a plurality of contact springs contact the plate and the filterhousing, respectively, so as to electrically connect the plate and thefilter housing to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of an embodiment of the inventivefilter arrangement.

FIG. 2 is an exploded perspective view of another embodiment of thefilter arrangement including a fan.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

As can be seen in FIG. 1, the invention involves a filter arrangementcomprised of a mounting plate 27, such as the wall of a device in acontrol cabinet, having an aperture 26 surrounded by a contactingsurface 24 with screw receptacles 25 or fastening holes. A contact frame23 comprised of electrically conductive material is inserted intoaperture 26 of mounting plate 27. A filter housing 10 having an outletside and an inlet side and a center opening is connected to contactframe 23. A filter mat 21 is placed in the opening in filter housing 10along with an electrically conductive grid 20 located in series airflowrelationship with filter housing 10 and filter mat 21. "Series airflowrelationship," as used herein, is defined as allowing the air to flowconcurrently through grid 20, filter housing 10 and filter mat 21.Finally, a lamellar screen 22 covers filter mat 21.

In a preferred embodiment of the invention, as shown in FIG. 2, a fan 16is attached to the inlet side of filter housing 10' and electricallyconductive grid 20 is positioned between filter housing 10' and fan 16.In this embodiment, fan 16 is secured to filter housing 10 through theuse of screws 19 that pass through housing 10 and fastening flange 15 offan 16. The contact frame 23, grid 20 and filter housing 10 providedwith an electrically conductive surface seals aperture 26 in anHF-impervious manner. In a more specific version of this embodiment, fan16 has an outlet and inlet side and the inlet side of fan 16 is coveredby a protective screen 18. In still another version, fan 16 projectsthrough both contact frame 23 and aperture 26 of mounting plate 27.

The grid 20 used in all versions of the embodiment involving a fan 16has a finer mesh than holding screen 12 used in the embodiment without afan 16. The grid 20 which also has a finer mesh than one of protectivescreens 18 that is connected to the outlet side of fan 16 can becomprised of plastic and be provided with an electrically conductivesurface.

In another aspect of the invention, filter housing 10 is constructed ofplastic in which electrically-conductive material is mixed or which hasbeen "metallized" or vapor-coated with a conductive substance so as tobe electrically conductive thereby allowing filter housing 10 andcontact frame 23 to be connected to each other in an electricallyconductive manner. In another embodiment of the invention, filterhousing 10 has a receptacle formed into its outlet side and filter mat21 and grid 20 are inserted into the receptacle.

The filter mat 21 and grid 20 are supported in housing 10 by means of aholding screen 12 which is constructed with a course mesh and isadvantageously constructed as one piece together with filter housing 10.A lamellar screen 22 covers the outside of the filter arrangement in aknown manner. According to one embodiment, contact frame 23 thatsupports the HF-shielding uses copper-beryllium. Because of this,aperture 26 in mounting plate 27 is rendered HF impervious (i.e., thefilter arrangement in aperture 26 is shielded in the direction ofmounting plate 27).

In yet another aspect of the invention, filter housing 10 has acircumscribing fastening flange with fastening bore holes 13 and screws14 passing through fastening bore holes 13 to secure the filter housing10 to mounting plate 27. In a specific version of such preferredembodiment, mounting plate 27 has a contact surface 24 surroundingaperture 26 and contact surface 24 contains a plurality of screwreceptacles 25 arranged around aperture 26.

In still another aspect of the invention, contact frame 23 projects intoaperture 26 of mounting plate 27. The first and second edges of each ofa plurality of contact springs 23.1 contact mounting plate 27 and filterhousing 10, respectively, so as to electrically connect mounting plate27 and filter housing 10 to one another.

Although the contacting surface of contact frame 23 is usually appliedto mounting plate 27, it can also be a part that is separate frommounting plate 27. For example, contacting surface 24 can be insertedinto aperture 26 of mounting plate 27 and connected to it in anelectrically conductive manner. Also, the electrical conductivity of thesurface of filter housing 10 and a plastic contact frame 23 can beachieved by other means such as through the use of plastic in which anelectrically-conductive material has been mixed.

A complete HF shielding of aperture 26 of the mounting plate 27 isalways totally achieved since mounting plate 27, contact frame 23 andfilter housing 10 are connected to grid 20 in an electrically conductivemanner thereby covering aperture 26 and shielding it.

While the principles of this invention have been described in connectionwith specific embodiments, it should be understood clearly that thesedescriptions are made only by way of example and are not intended tolimit the scope of the invention.

What is claimed:
 1. A filter arrangement comprised of:a mounting platehaving an aperture; an electrically conductive contact frame extendinginto the aperture; a filter housing connected to the contact frame andhaving an outlet side, an inlet side and a central opening; a filter matin the opening in the filter housing; an electrically conductive grid inseries airflow relationship with the filter housing and the filter mat;and a lamellar screen over the filter mat.
 2. The filter arrangement ofclaim 1 wherein:a fan is attached to the inlet side of the filterhousing; and the electrically conductive grid is between the filterhousing and the fan.
 3. The filter arrangement according to claim 1wherein:the filter housing is constructed of plastic; and the plastic iscoated with an electrically conductive material.
 4. The filterarrangement according to claim 1 wherein:the filter housing has areceptacle formed in the outlet side; and the filter mat and grid areinserted into the receptacle.
 5. The filter arrangement according toclaim 1 wherein:the filter housing includes a circumscribing fasteningflange having fastening bore holes; and screws extending through thefastening bore holes secure the filter housing to the mounting plate. 6.The filter arrangement of claim 5 wherein:the mounting plate has acontact surface surrounding the aperture; and the contact surfaceincludes a plurality of screw receptacles arranged around the aperture.7. The filter arrangement of claim 1 wherein:the inlet side of thefilter housing is covered by a mesh holding screen; and the mesh holdingscreen supports the grid and filter mat.
 8. The filter arrangementaccording to claim 7 wherein the mesh holding screen is constructed inone piece together with the filter housing.
 9. The filter arrangementaccording to claim 2 wherein:the fan has an outlet and inlet side; andthe inlet side of the fan is covered by a protective screen.
 10. Thefilter arrangement of claim 1 wherein each of a plurality of contactsprings extend between the mounting plate and the filter housing,thereby electrically connecting the mounting plate and filter housing.11. The filter arrangement of claim 2 wherein the fan projects throughthe contact frame and the aperture of the mounting plate.